Compare Strings

Unlike other types of data, text data has very few restrictions on the kinds of values that appear in a cell. In the application, this data is typically inferred as String data type. As a result, finding string values that mean the same thing can be a challenge, as minor differences in their content or structure can invalidate a match.

This section provides some methods for comparing strings.

Some target systems may impose limits on the lengths of imported values. For more information on managing the lengths of your strings, see Manage String Lengths.

Find Substrings

You can use the following functions to locate sub-strings that are part of a column's value.

You can nest function expressions inside of the EXACT reference to eliminate common and perhaps not useful differences between strings. In the following transformation, a value of true is inserted into the matches column, if colA and colB are exact matches, after whitespace and case differences have been removed:

Doublemetaphone matching

The platform also supports the doublemetaphone algorithm for fuzzy matching. This algorithm provides mechanism for proximity matching; the DOUBLEMETAPHONEEQUALS function supports an optional second parameter to define the strength of the algorithm.

This algorithm works by generating two separate encodings for each string: a primary encoding and a secondary encoding. You can experiment with these encodings using the DOUBLEMETAPHONE function. See DOUBLEMETAPHONE Function.

This algorithm can be applied to compare two strings, as in the following transformation.

Transformation Name

New formula

Parameter: Formula

DOUBLEMETAPHONEEQUALS(colA,colB,'strong')

Parameter: New column name

matches

The first two parameters of the function are the string literals, column references, or functions returning strings to compare.

The third parameter is optional. It determines the level of matching required to return true. Options:

Match threshold

Description

'strong'

Both primary encodings must match.

'normal'

At least one primary encoding must match either of the other string's encodings

Compare Strings

For string values, you can use the string comparison functions to check how strings compare using Latin collation settings.

Tip: Any column can be converted to String data type to use these functions.

Collation refers to the organizing of written content into a standardized order. String comparison functions utilize collation rules for Latin. A summary of the rules:

Comparisons are case-sensitive.

Uppercase letters are greater than lowercase versions of the same letter.

However, lowercase letters that are later in the alphabet are greater than the uppercase version of the previous letter.

Two strings are equal if they match identically.

If two strings are identical except that the second string contains one additional character at the end, the second string is greater.

A normalized version of a letter is the unaccented, lowercase version of the letter. In string comparison, it is the lowest value of all of its variants.

a is less than ă.

However, when compared to b, a = ă.

The set of Latin normalized characters contains more than 26 characters.

This table illustrates some generalized rules of Latin collation.

Order

Description

Lesser Example

Greater Example

1

whitespace

(space)

(return)

2

Punctuation

'

@

3

Digits

1

2

4

Letters

a

A

5

A

b

Resources:

NOTE: In the following set of charts (linked below), the values at the top of the page are lower than the values listed lower on the page. Similarly, the charts listed in the left nav bar are listed in ascending order.